1. Technical Field
The present invention relates to a connector-type optical transceiver using a silicon-on-insulator (SOI) optical waveguide, and more particularly to an optical transceiver provided with a detachable connector and adapted to transmit and receive optical signals using an SOI optical waveguide.
2. Description of the Prior Art
The widespread exchange of information (e.g., image, text and audio data) and Internet communication, which is expected to continue to expand to great proportions, has greatly increased the demand for high-rate data transmission and reception. To this end, the incorporation of ultra-high-rate data communication networks using fiber optic transmission lines (hereinafter referred to as xe2x80x9coptical fibersxe2x80x9d) has been actively pursued.
Such optical communication networks are basically made up of optical fibers, which are media for transmitting optical signals, an optical transceiver module for converting an optical signal into an electrical signal and vice versa, and components for distributing, amplifying and modulating transmission signals. The optical transceiver module is the most important component in constructing an optical communication system. The cost of these modules, however, hinders the widespread usage and incorporation of optical communication networks. There two primary factors interfering with cost reduction: technical difficulty in aligning the optical fiber with a laser diode, which requires 1 xcexcm tolerances, and the enormity of the investment costs needed for the necessary mass-production equipment. In particular, the costs required to implement a packaging process adapted for the alignment between the optical fiber and laser diode forms 70xcx9c80% or more of the total manufacturing costs of the optical transceiver module.
Alignment between the laser diode and optical fiber is achieved using one of two basic methods. These are active alignment and passive alignment.
In the active alignment method, the coupling position is determined by peaking the amount of laser-diode light incident to a juxtaposed optical fiber. The laser diode and optical fiber are then fused at the determined coupling position using a laser welder or bonded using an epoxy adhesive.
In the passive alignment method, the coupling position between the laser diode and optical fiber is determined without activating the laser diode. The passive alignment method may be achieved by identifying the respective positions of the laser diode and optical fiber using an image processing apparatus, or by a flip-chip bonding method which makes use of a phenomenon whereby molten metal exhibits an advantageous surface tension. Another method has also been proposed in which a silicon bench is micro-machined to have a specified three-dimensional structure using photolithography, to allow optical devices having different functions to be integrated on the same bench. Recently, the use of such passive alignment methods has increased due to their shorter processing times and lower costs than those of the active alignment method.
FIG. 1 shows a conventional connector-type optical transceiver module using optical fibers. As shown in FIG. 1, the optical transceiver module uses a connector 1 which is known as a mechanically transferable reinforced jacket (MT-RJ). An external connecting terminal (not shown) is connected to the connector 1 while being guided by a pair of guide pins 15 provided at the connector. Accordingly, an optical path established by optical fibers 2, which extend through the connector 1, is brought into precise alignment with the external connecting terminal.
The conventional transceiver module is fabricated by arranging optical fibers 2 and optical devices (e.g., a laser diode, a photo diode, a monitor photo diode and/or an SOI waveguide) on a silicon bench 3 in respective V-shaped micro-grooves of the silicon bench, such that the optical devices and optical fibers are aligned and bonded on the silicon bench. To avoid an optical coupling loss, the optical fibers 2 should be polished at their ends, to have mirror-like surfaces.
However, the optical fibers 2 used in the conventional optical transceiver module have an outer diameter of 125 xcexcm and therefore experience difficulty in manipulation and handling. Furthermore, polishing the cut ends of the optical fibers 2 is an expensive operation, and the optical fibers are separately bonded to the silicon bench 3. Such exacting requirements, together with the high costs, have impeded efforts to mass-produce the transceiver modules.
In order to solve the difficulty in processing the optical fibers 2, a planar light-wave circuit (PLC) method has been proposed, in which a silica waveguide is used in place of the optical fibers. The PLC method uses frame hydrolysis deposition method to micro-machine a silica PLC board to have an alignment structure for arranging and aligning optical devices on the PLC board. However, the frame hydrolysis deposition process is expensive and therefore hinders cost reduction efforts.
Meanwhile, the passive alignment method using the conventional flip-chip bonding technique makes it difficult to simultaneously bond a variety of optical devices on the same silicon bench. However, flip-chip bonding, which achieves the alignment of optical devices using the surface tension of molten solder, requires special equipment to implement an anti-oxidation effect upon melting the solder, which is expensive but necessary to avoid a reduction in surface tension due to oxidation. Without the anti-oxidation effect, adequate surface tension is lost which results in the loss of a desired position control.
In order to solve these problems, a new method has been proposed in which optical devices are temporarily bonded onto desired positions using ultrasonic waves, while maintaining a positional accuracy of several tens of micrometers, and are then metal-bonded in a batch fashion.. Ultrasonic bonding, however, is a time-consuming operation, and damage to the optical devices is likely, due to the vibratory impact applied thereto during the bonding process.
Therefore, an object of the invention is to solve the above-described problems involved in the conventional methods, and to provide a connector-type optical transceiver which can be fabricated at low cost.
Another object of the invention is to provide a connector-type optical transceiver which can be easily fabricated using an automated process.
Yet another object of the invention is to provide an optical transceiver fabricated using a planar SOI optical waveguide instead of optical fibers.
Still another object of the invention is to provide an optical transceiver which achieves a reduction in the number of, components used to constitute an optical transceiver module and a simplified manufacturing process.
Still yet another object of the invention is to provide an optical transceiver which realizes each of the above objects without using an MT-RJ connector fixedly mounted to the silicon bench.
In accordance with the present invention, these objects are accomplished by providing a connector-type optical transceiver comprising: a plurality of optical devices; a silicon-on-insulator (SOI) optical waveguide including a silicon substrate, a single crystalline silicon layer whose upper surface is provided with waveguide portions, and a silica thin layer interposed between the silicon substrate and the single crystalline silicon layer, to prevent light passing through the waveguide portions from being diffused; and a silicon bench whose upper surface is provided with U-shaped recesses receiving the optical devices and the SOI optical waveguide, while being aligned to form optical paths.
In accordance with an embodiment of the present invention, the silicon bench has V-shaped grooves extending longitudinally along the silicon bench, receiving guide pins adapted to guide an external connecting terminal to be connected to the silicon bench.
In accordance with an embodiment of the present invention, each of the waveguide portions comprises a longitudinal protrusion, integrally formed with and protruding from the upper surface of the single crystalline silicon layer, to allow an optical signal to pass.
The optical transceiver of the present invention is configured such that a silicon bench is formed with V-shaped grooves, to receive guide pins for connection to an external connecting terminal.